Preparation of Sulfonamides from Sodium Sulfonates: Ph3P ⋅ Br2 and Ph3P ⋅ Cl2 as a Mild Halogenating Reagent for Sulfonyl Bromides and Sulfonyl Chlorides - Kataoka, Tadashi; Iwama, Tetsuo; Setta, Tomofumi; Takagi, Atsuko (Synthesis, 1998)